Conventional rotary floor maintenance devices have used gear boxes, belt drives and the like to couple the motor shaft to the rotary brush. Examples of conventional rotary floor maintenance devices are disclosed in the following U.S. Pat. Nos. 1,485,680 to Hughes; 1,588,157 to Beach; 2,079,946 to Myers; 3,412,415 to Brab; 4,330,897 to Tucker; 4,360,939 to Krumm; and 4,365,377 to Todd.
Rotary floor maintenance devices with gear boxes are relatively noisy, and require periodic lubrication. Because of the noise, machines of this type are often distracting when operated during normal working hours in a business environment. The problem becomes particularly acute in hospitals where the permissible noise level is generally limited to 65 db.
Gaudry in U.S. Pat. No. 3,469,470 attempted to reduce the noise level of gear boxes for rotary floor maintenance devices by replacing metal gears with gears made of synthetic resin materials, such as nylon, acetate, polycarbonate, or phenolic thermoplastic resins. Although noise levels are reduced by the use of synthetic resin gears, such gears are not as durable as metal gears. Also, the use of a gear box, whether the gears be made of metal or synthetic resin, reduces the overall efficiency of the rotary floor maintenance device.
Gear boxes are generally required in order to supply high torque at low speed to the rotary brushes. Without a gear box or the like, the electrical current which would be required to operate a floor maintenance device motor at sufficient torque and relatively low speed would exceed the 20 amp trip current of the circuit breaker protecting the circuit from which the floor maintenance device is being supplied electric power.
Another solution is to use an electric motor having greater torque at lower speeds. However, this solution results in an increase in the physical size of the motor, particularly the height. Since the motors are typically mounted directly on top of the rotary brush skirt housing, any increase in motor size also increases the height of the machine operating head. Since it is desirable to use rotary floor maintenance devices under furniture and cabinet ledges, it is necessary to keep the overall height of the machine operating head as low as possible. Therefore increasing the overall height of the machine operating head detracts from the general utility and desirability of the machine. Various arrangements for reducing the height of the operating head have been proposed and used. For instance, U.S. Pat. No. 2,079,946 to Myers discloses a construction whereby the motor is mounted to the rear of the operating head. U.S. Pat. No. 3,518,712 to Berger discloses a motor mounted on the handle. Although both of the aforementioned designs reduce the overall height of the operating head, both relocate the overall center of gravity of the machine in a way which causes the overall stability of the machine to be reduced.
Another problem which has been encountered with conventional machines is that liquid is splashed into the motor housing and accumulates therein. This can be a personnel safety hazard, as well as being destructive to the motor. Despite the adverse consequences of liquid accumulation in the motor housing, the design of a motor support structure which will allow drainage appears not to have been previously attempted. This feature is particularly important when the rotary floor maintenance device is used in a scrubbing mode. In this mode water and detergent solution may be splashed into the motor housing.
Control of conventional rotary floor maintenance devices can easily be lost if they are started inadvertantly. Such a runaway device can potentially cause injury and damage. One way to prevent inadvertant operation is to put a safety interlock in the handle, thereby requiring two independent actions by an operator, rather than one, to operate the machine. In this way, the likelihood of inadvertant operation is greatly reduced. U.S. Pat. No. 3,412,415 to Brab descloses one type of safety interlock. Brab utilizes a bar linkage to actuate a microswitch which controls the energization of the machine. One member, connected to a safety interlock actuator, defeats a stop on a bar linkage when depressed, to allow the microswitch to be revolved and consequently actuated by a linkage member. Linkage devices such as the one disclosed in the Brab patent, because of the journalled connection of linkage members, require periodic maintenance including lubrication. This may require disassembly of the interlock system. Once disassembled, maintenance personnel may decide to defeat the interlock to preclude the need for further periodic maintenance. Also, three and four bar linkages, such as the one disclosed by Brab, require coplanar alignment for proper operation. Improper and forceful actuation of the interlock can cause misalignment and therefore the need for additional maintenance.